Ars has reviewed the brand new iMac. They conclude: "The Intel Macs are fast, the majority of apps have been released as Universal Binaries, and Apple's product line - including the new iMac - is in a good place. The iMac is also competitive on price with other all-in-one PCs, so if you absolutely love the all-in-one form factor, the iMac is one of lower-priced options available. If you've been holding on to your Power PC Mac and waiting for the right time to make the big switch to Intel, the appearance of the new iMac marks an excellent opportunity." CNet also has a review.

Metal conducts heat far better than plastic. Add to that: dark-colored surfaces radiate heat much better than white or shiny surfaces. If the back of that iMac is actually black anodized aluminum (not black plastic), then I'm sure it does a *far* better job of pulling heat away from the internal components than the previous white plastic back panel.